Powdered medication is typically administered orally to a person as a tablet or capsule, or as an inhalant. The prior art discloses a number of techniques for administering doses of inhalable dry powders to the lungs of a patient. Generally, inhalers are mechanical systems that generate a metered cloud of medicament powder for inhalation by a patient. Many of these prior art inhaler devices use chlorofluorocarbon (CFC) gas to facilitate generating a metered cloud of medicament for inhalation. However, since CFCs are no longer used in consumer products, other techniques for generating the medicament cloud have been explored.
One example of a non-CFC, prior art inhaler is disclosed in U.S. Pat. No. 4,811,731 issued Mar. 14, 1989 (the "'731 patent"). This patent discloses an inhaler that contains a plurality of measured doses of medicament stored in a blisterpack. Upon use, one of the blisters in the blisterpack is punctured and a patient inhales the medicament from the punctured blister via a mouthpiece of the inhaler. In the '731 patent, the medicament dosage is measured and deposited in each blister of the blisterpack using conventional, mechanical measuring and depositing techniques. Detrimentally, such mechanical deposition techniques do not apply repeatable doses of medication into each blister of the blisterpack. Typically, some of the medicament adheres to the mechanical deposition system and, as such, reduces the amount of medication deposited into a given blister. The degree of adhesion depends upon the environment in which the deposition is conducted, e.g., the ambient humidity, temperature and the like. Since a mechanical deposition process is used to apply medicament to other orally administrable platforms, the same dose variation evident in inhaler doses occurs for other platforms as well. As such, a more accurate technique is needed in the art for depositing medication into any orally administrable platform including inhalers, tablets, capsules, suppositories, and the like.
An example of a technique for producing orally administered medication tablet or capsule form is disclosed in U.S. Pat. No. 4,197,289 issued Apr. 8, 1980. This technique utilizes an electrostatic deposition process for depositing a medicament upon an edible substrate that is referred to in the '289 patent as a "web". Using a conventional corona charging technique, this process continuously charges the web as the web moves past the charging element. Thereafter, the web passes though a compartment containing a medicament cloud. The medicament in the cloud is attracted to the charged web and becomes deposited thereupon, i.e., the web becomes "loaded". A spectroscopic monitoring system determines the amount of medication that has been deposited on the web and generates a control signal that regulates the amount of medicament within the cloud chamber. As such, the '289 deposition technique uses an active feedback system to regulate the deposition process. To complete the process, the loaded web is cut into individual units that can be combined with one another to define a medicament dose, e.g., a particular number of individual web units defines a single dose of the medication. The combined units are then encapsulated to form individual, orally administrable doses of medication.
A disadvantage of the '289 technique is the requirement for an active feedback system to control the deposition process. Such systems are typically complex and require an integrated medicament measuring system to generate the control signals, e.g., such as the spectroscopic monitoring system of the '289 patent. In using a feedback system, the '289 technique attempts to uniformly deposit the medicament across the entire web. Dosage control is therefore accomplished not by changing the deposition quantity upon the web, but rather by combining a number of web units to form a dose. As such, the dosage control process is unduly complicated. For example, to generate a uniform deposit of medicament, the electrostatic charge on the web must be uniform, the rate at which the web passes the charging element and the cloud compartment must be constant, and the feedback system must accurately measure the amount of drug on the web and accurately control the amount of medication in the cloud compartment. Thereafter, assuming the medication was uniformly deposited on the web, the web must be accurately cut into units that can be combined and encapsulated to form doses of the medication. Each of the encapsulated doses is supposed to contain the same amount of medication as all other doses. However, such a complicated process is prone to error.
Therefore, a need exists in the art for a medicament deposition process that electrostatically deposits specific quantities of dry powder medication at particular locations on a dielectric substrate. Additionally, a need exists in the art for a technique for quantifying an amount of electrostatic charge accumulated on the substrate and to use the quantified charge value to regulate the quantity of medicament deposited on the substrate.